import Constant.constant;
import utils.IndexException;

public class LinkedList implements IList {
    //1.定义一个内部类
    static class ListNode{
        public int val;
        //类型写成了String,应该是ListNode的
        public ListNode prev;
        public ListNode next;

        public ListNode(int val) {
            this.val = val;
        }
    }
    public ListNode head;

    //这个就要给个尾了
    public ListNode last;




    @Override
    public void addFirst(int data) {
        if(head==null){
            ListNode node=new ListNode(data);
            head=last=node;
        }else{
            ListNode node=new ListNode(data);
            node.next=head;
            head.prev=node;
            head=node;
        }

    }

    @Override
    public void addLast(int data) {
        if(head==null){
            ListNode node=new ListNode(data);
            //写成了node=last=null了
            head=last=node;
        }else{
            ListNode node=new ListNode(data);
            last.next=node;
            node.prev=last;
            //这里要注意
            last=last.next;
        }

    }

    @Override
    //在LinkedList中找到对应的cur，然后再cur之前插入
    public void addIndex(int index, int data) {
        int len=size();
        if(index<0||index>len){
            String msg= constant.INDEX_IS_WRONG+index;
            throw new IndexException(msg);
        }
        if(index==0){
            addFirst(data);
        }else if(index==len){
            addLast(data);
        }else{
            ListNode node=new ListNode(data);
            ListNode cur=findIndex(index);
            node.next=cur;
            cur.prev.next=node;
            node.prev=cur.prev;
            cur.prev=node;
        }

    }
    //在LinkedList中找到对应的cur
    private ListNode findIndex(int index){
        if(head==null){
            return null;
        }else{
            ListNode cur=head;
            while(index!=0){
                cur=cur.next;
                index--;
            }
            return cur;
        }
    }

    @Override
    public boolean contains(int key) {
        if(head==null){
            return false;
        }else{
            ListNode cur=head;
            while(cur!=null){
                if(cur.val==key){
                    return true;
                }else{
                    cur=cur.next;
                }
            }
            return false;
        }

    }

    @Override
    public void remove(int key) {
        //1.先判断链表是否为空
        if(head==null){
            return;
        }else{
            ListNode cur=head;
            while(cur!=null){
                if(cur.val==key){
                    //1.考虑头删的情况
                    if(cur==head){
                        head=head.next;
                        //考虑如果链表中只有一个节点的情况
                        if(head!=null){
                            head.prev=null;

                        }
                        }else{
                        cur.prev.next=cur.next;//尾巴节点和中间节点共用
                        if(cur.next==null){//尾节点
                            last=last.prev;

                        }else{//中间节点
                            cur.next.prev=cur.prev;
                        }
                    }
                    return;

                }
                cur=cur.next;
            }
        }


    }

    @Override
    public void removeAllKey(int key) {
        if(head==null){
            return;
        }else{
            ListNode cur=head;
            while(cur!=null){
                if(cur.val==key){
                    if(cur==head){
                        head=head.next;
                        //只有一个节点的情况要考虑
                        if(head!=null){
                            head.prev=null;
                        }
                    }else{
                        cur.prev.next=cur.next;
                        if(cur.next==null){
                            last=last.next;
                        }else{
                            cur.next.prev=cur.prev;
                        }
                    }
                }
                cur=cur.next;
            }
        }

    }

    @Override
    public int size() {
        if(head==null){
            return 0;
        }else{
            ListNode cur=head;
            int count=0;
            while(cur!=null){
                cur=cur.next;
                count++;
            }
            return count;
        }


    }

    @Override
    public void display() {
        if(head==null){
            return;
        }else{
            ListNode cur=head;
            while(cur!=null){
                System.out.print(cur.val+" ");
                cur=cur.next;
            }
            System.out.println();
        }


    }

    @Override
    public void clear() {
        if(head==null){
            return;
        }else{
            ListNode cur=head;
            while(cur!=null){
                ListNode curN=cur.next;
                cur.prev=null;
                cur.next=null;
                cur=curN;
            }
            head=last=null;//最后要把head和last置为null
        }


    }
}
